Ruthenium atomic properties

The crystal structures of the Ru(Et2Dtc)3G (268) and Ru(Me2Dtc)3I3 (435) complexes have been determined. On both, the Ru(IV) coordination geometry is pentagonal bipyramidal (Fig. 39) (Table XX). The ruthenium atoms in the ethyl derivative are pendant on infinite chains of iodine atoms in the lattice. This observation and the unusual golden color of the complex suggest that the crystals of this compound may possess interesting electrical properties. 

To prepare [2]metallocenophanes that are even more strained than [2]ferrocenophanes 30, species with a larger ruthenium atom in the place of iron have been synthesized (81). Such [2]ruthocenophanes would be expected to possess much greater ring-tilt angles moreover, because ruthenocene is known to possess significantly different electrical properties compared to ferrocene, modified polymer properties would be anticipated (57). 

Ruthenium complexes were among the first catalysts employed for controlled radical polymerization via ATRP mechanism (i, 2). One the one hand, this happened due to the fact that ATRP process originates from Kharash reaction of radical addition (5), which is catalyzed by complexes of this metal. On the other hand, this was associated with the unical properties of ruthenium atom, particularly the ability to assume different oxidation states and various coordination geometries 4-6). 

Rose and Wilkinson, by treatment of the methanolic blue solutions with various cations, have trapped out stable solids of composition M[Ru5Cl,2] (M = Fe(bipy)3 , Ru(bipy)3 , [C6H4(CH2PPh3)2] " and proposed structure (359). The ESR spectra of these materials are essentially identical to those of the blue solutions in various solvents, so it is reasonable to assume that the ion present in the solids is also present in the blue solutions. However, the ESR spectrum and magnetic properties of (359) =1.3 BM per five ruthenium atoms) are not consistent with what... 

The substitution of the iron atom by ruthenium has been performed to evaluate the importance of the redox properties of iron, while maintaining the presence of metallocene in the side chain of the molecule [60]. The molecule was named ruthenoquine (RQ). Methyl ruthenoquine (MeRQ) features both modifications (i.e., replacement of the iron atom by a ruthenium atom and alkyl substitution of nitrogen atom 11) [60]. This molecule is not able to establish the intramolecular hydrogen bond and is also not able to produce the reactive oxygen species (ROS) in oxidizing conditions of the digestive vacuole. 

Petrii and Entin [54, 57, 78, 150, 180, 243] investigated the adsorption and electrochemical characteristics of platinum and ruthenium alloys in detail. The optimum alloy compositions for oxidation of methanol at various temperatures were determined, the anodic oxidation reactions of various compounds of the alloys were investigated, the stability of the alloys after prolonged use was investigated, and the characteristics of platinum— ruthenium alloys prepared by various methods (skeletal electrodes, electro-lytically mixed deposits on a platinum and titanium carbide bases, powders deposited by sodium borohydride, smooth alloys) were compared. It was found that heat treatment of platinum - ruthenium alloys at 800 C in an atmosphere of inert gas led to loss of their high catalytic properties and formation of catalysts which behave similarly to platinum. This phenomenon is explained by diffusion of ruthenium atoms from the surface layer into the volume. 

As is known [25], on palladium, a molecular adsorption of CO is predominant, which determines its high selectivity with respect to methanol. The decrease in palladium activity towards methanol synthesis can hardly be explained by the effect of ruthenium dilution, since molecular adsorption of CO and its hydrogenation to CH3OH can, most probably, proceed on smaller centers than are required for dissociative adsorption of CO. This phenomenon may be accounted for by the ligand effect, that is, by the change of electronic properties of a palladium atom due to the presence of ruthenium atoms in its first coordination sphere. 

Almost every metal atom can be inserted into the center of the phthalocyanine ring. Although the chemistry of the central metal atom is sometimes influenced in an extended way by the phthalocyanine macrocycle (for example the preferred oxidation state of ruthenium is changed from + III to + II going from metal-free to ruthenium phthalocyanine) it is obvious that the chemistry of the coordinated metal of metal phthalocyanines cannot be generalized. The reactions of the central metal atom depend very much on the properties of the metal. 

The results of the EXAFS studies on osmium-copper clusters lead to conclusions similar to those derived for ruthenium-copper clusters. That is, an osmium-copper cluster Is viewed as a central core of osmium atoms with the copper present at the surface. The results of the EXAFS investigations have provided excellent support for the conclusions deduced earlier (21,23,24) from studies of the chemisorption and catalytic properties of the clusters. Although copper is immiscible with both ruthenium and osmium in the bulk, it exhibits significant interaction with either metal at an interface. 

Since ruthenium and rhodium are neighboring elements in the periodic table, a closer comparison of the properties of ruthenium-copper and rhodium-copper clusters is of interest (17). When we compare EXAFS results on rhodium-copper and ruthenium-copper catalysts in which the Cu/Rh and Cu/Ru atomic ratios are both equal to one, we find some differences which can be related to the differences in miscibility of copper with ruthenium and rhodium. The extent of concentration of copper at the surface appears to be lower for the rhodium-copper clusters than for the ruthenium-copper clusters, as evidenced by the fact that rhodium exhibits a greater tendency than ruthenium to be coordinated to copper atoms in such clusters. The rhodium-copper clusters presumably contain some of the copper atoms in the interior of the clusters. 

Because of- the similarity in the backscattering properties of platinum and iridium, we were not able to distinguish between neighboring platinum and iridium atoms in the analysis of the EXAFS associated with either component of platinum-iridium alloys or clusters. In this respect, the situation is very different from that for systems like ruthenium-copper, osmium-copper, or rhodium-copper. Therefore, we concentrated on the determination of interatomic distances. To obtain accurate values of interatomic distances, it is necessary to have precise information on phase shifts. For the platinum-iridium system, there is no problem in this regard, since the phase shifts of platinum and iridium are not very different. Hence the uncertainty in the phase shift of a platinum-iridium atom pair is very small. 

The layer of titanium and ruthenium oxides usually is applied to a titanium substrate pyrolytically, by thermal decomposition (at a temperature of about 450°C) of an aqueous or alcoholic solution of the chlorides or of complex compounds of titanium and rathenium. The optimum layer composition corresponds to 25 to 30 atom % of ruthenium. The layer contains some quantity of chlorine its composition can be written as Ruq 2sTio 750(2- c)Cl r At this deposition temperature and Ru-Ti ratio, the layer is a poorly ordered solid solution of the dioxides of ruthenium and titanium. Chlorine is completely eliminated from the layer when this is formed at higher temperatures (up to 800°C), and the solid solution decomposes into two independent phases of titanium dioxide and ruthenium dioxide no longer exhibiting the unique catalytic properties. 

A number of mechanistic pathways have been identified for the oxidation, such as O-atom transfer to sulfides, electrophilic attack on phenols, hydride transfer from alcohols, and proton-coupled electron transfer from hydroquinone. Some kinetic studies indicate that the rate-determining step involves preassociation of the substrate with the catalyst.507,508 The electrocatalytic properties of polypyridyl oxo-ruthenium complexes have been also applied with success to DNA cleavage509,5 and sugar oxidation.511... 

Like rhenium and ruthenium it crystallizes in a closest packed hexagonal lattice with the metal atoms having the coordination number 12. In Table 2 some properties of technetium are compared with those of manganese and rhenium. 

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